1. Field of the Inventions
The present inventions relate to power transmitting apparatuses for switching between 2-wheel and 4-wheel modes and locking and unlocking differential devices.
2. Description of the Related Art
Four-wheel buggies, also known as “ATVs” (All Terrain Vehicles), usually include power transmitting apparatuses for connecting and disconnecting power from an engine to the front wheels, which are not-driven wheels, and also switching between 2-wheel and 4-wheel drive modes. Such a vehicle is disclosed in Japanese Laid-open Patent Publication No. 191768/2003.
Generally, the power transmitting apparatus is provided with a differential mechanism (differential gear set) to provide smooth turning of vehicle by absorbing the difference of rotation between left and right wheels. Japanese Laid-open Patent Publication No. 509409/1994 discloses another type of differential system that does not a differential gear set.
Some known designs can limit the differential action of one wheel by incorporating a power transmitting apparatus provided with means for locking the differential mechanism (differential-locking means) in order to prevent a reduction of driving torque under circumstances in which one of left and right wheels of vehicle would be mired in a slippery road such as mud. A more recently proposed design of a power transmitting apparatus include a motor for connecting and disconnecting the driving force and locking and unlocking of a differential mechanism.
For example, one prior art power transmitting apparatus includes an electric motor arranged in either of the left or right sides of a case forming a box of the power transmitting apparatus. The connection and disconnection between an input shaft connected to an engine and an output shaft connected to a front wheel as well as the locking and unlocking of a differential mechanism are performed by actuating a fork connected to an actuator driven by the electric motor.
Japanese Laid-open Patent Publication No. 324719/2005 discloses a driving device for actuating a fork that connects and disconnects or that performs locking and unlocking of the operating device. In this system, the driving shaft engaged by the operating device for actuating the fork, is projected from a sub case (containing case). In addition the sub case, which forms a case for the driving means, is sealed and structured so that the driving force of the motor can be transmitted to the operational means via the driving shaft by engaging the operational means with an end of the driving shaft projected from the sub case.
More specifically, Japanese Laid-open Patent Publication No. 324719/2005 discloses a rotational member (driving gear 21) driven by an electric motor and formed with a contacting member, a coil spring (23) arranged on the rotational member, a connecting member (rotation holding member 24) arranged to be abutted by one end of the coil spring and rotated by the rotational member via the coil spring, a driving shaft (output shaft 22) rotatable relative to the rotational member and rotated by the rotational member, a stay (holder 28) engaged by the driving shaft in its rotational direction and formed with a contacting member, and a substrate (circuit substrate 40) formed with conducting patterns able to form predetermined electric circuits in accordance with the rotational angles of the rotational member and the driving shaft.
In the power transmitting apparatus of the prior art, the assembly of a driving means has been performed by mounting the connecting member and the rotational member caulked on the driving shaft after the stay had been mounted within the sub case and the substrate covering the stay had been mounted. A tip end of the driving shaft is formed as a “D” shaped cut (“D” shaped cross-section) and a through aperture having a configuration corresponding to the “D” shaped driving shaft is formed in the stay. The stay is anchored in the rotational direction of the driving shaft by inserting the tip end of the driving shaft integral with the connecting member into the rotational member and the substrate and then by anchoring the stay on the driving shaft in its rotational direction with anchoring the through aperture of the stay to the “D” cut shaft of the driving shaft. Thus a predetermined phase (relative rotational angle) can be obtained between the stay and the driving shaft.